Nicolas, I know that posix_spawn exists now in Solaris.
But I measured that it has no benefit over the traditional vfork and
exec sequence of calls, but the authors of posix_spawn designed it to
be an improvement if *implemented* in the kernel. The lack of
performance difference between posix_spawn and vfork,exec and the
*very* bad performance of vfork,exec on Solaris - compared to Linux on
the same hardware, where 2.6.25.20-0.5-default can spawn utilities al
most 70% faster than Opensolaris B134 - has lead to my request to find
some one to try and improve the situation.
Olga
2010/7/14 Nicolas Williams <nicolas.willi...@oracle.com>:
> On Wed, Jul 14, 2010 at 01:50:39AM +0200, ольга крыжановская wrote:
>> My concern is not threading, not yet, until ksh93's multi thread
>> support lands in Solaris.
>> My concern is that fork and exec do double work or fork does jobs
>> which are then un done by exec again, but I can only speak for the BSD
>> implementation of fork and exec, not Solaris.
>> A posix_spawn system call would eliminate much of this madness.
>
> Olga,
>
> posix_spawn(3C) exists _now_ in Solaris, and it uses vforkx(2).
>
> vforkx(2), like vfork(2), doesn't copy/COW the parent's address space,
> but it does have to stop the parent's threads as a trade-off. The
> address space COW/copy of traditional fork is almost certainly the most
> expensive part of forking, which is precisely why posix_spawn(3C) uses
> vforkx(2) under the covers.
>
> A posix_spawn(2) system call would be able to save only the work of
> stopping, and subsequently resuming the parent process' threads, and a
> few syscall traps for the fcntl(2) and a few other system calls that
> posix_spawn(3C) has to make.
>
> The question is: is there a real problem here? Or is this just an
> imperfection that has caught your eyes but which might not actually be a
> real problem?
>
> Again, I could see that Java apps, Firefox and a handful of other
> applications could benefit from a posix_spawn(2), but I suspect these
> apps spawn children rarely enough that a user-land posix_spawn() is not
> a problem.
>
> My advice is: worry about real problems.
>
> Nico
> --
>
--
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